Drilling machine having rotary tools

ABSTRACT

A drilling machine comprising: a frame; at least one pair of rotary drilling tools having substantially the same axis of rotation; and a support assembly secured to the frame and supporting said pair of tools in rotation, said support assembly presenting an edge facing the cutting face and extending between the tools of said pair of tools, said machine further comprising: means mounted on said support assembly for creating at least one jet of liquid at very high pressure directed towards the cutting face between the action zones of said pair of tools; whereby said jet of liquid at very high pressure breaks up the ridge which forms in the cutting face between the action zones of said pair of rotary tools.

The present invention provides a drilling machine of the type comprisinga frame, and at least one pair of rotary drilling tools mounted on theframe, the rotary drilling tools presenting substantially the same axisof rotation.

BACKGROUND OF THE INVENTION

A particular example of that type of known machine, usually referred toas a “cutter”, is described below with reference to accompanying FIGS. 1to 3, in order to better understand the problems that can arise fromusing such a machine.

FIG. 1 shows a drilling vehicle 10 constituted mainly by a platform 12equipped with a jib 14 having a drilling machine 16 suspended from itstop end 14 a by means of cables 18. The drilling machine 16 comprises aframe 20 with two pairs of rotary drilling tools or cutters 22 and 24mounted at its bottom end. Each pair of drilling tools 22 or 24 isconstituted by two drilling tools 26 and 28, as can be seen more clearlyin FIG. 3, the drilling tools being rotatably mounted about axes whichusually coincide, the common axis being referenced 30. Furthermore, thetwo pairs of tools have parallel axes of rotation. More precisely, eachpair of tools is rotatably mounted in a support plate 32 secured to thebottom end 20 a of the frame of the drilling machine.

The drilling vehicle also includes a flexible hose 34 associated withsuction orifices 36 and with a suction pump 38 for sucking up thecuttings resulting from the action of the drilling tools. The drillingmachine also includes hydraulic supply hoses for hydraulically poweringthe motors driving the pairs of rotary tools 22 and 24.

As can be seen more clearly in FIG. 3, the presence of the support plate32 between the drilling tools 26 and 28 of a same pair leaves a gap ebetween the action zones of the drilling tools on the cutting face 40.The gap 39 leads to a ridge 42 being formed in the cutting face. Inaddition, the plate 32 presents an edge 32 a that is usuallysemi-circular, semi-oval, or polygonal in shape.

It should be understood that while the pairs of drilling tools are beingactuated, the formation of the ridge 42 opposes or hinders progress ofthe drilling tool, especially if the ground that is being drilled isrelatively hard.

The ridge 42 typically presents a height of about 250 millimeters (mm)and a width of about 70 mm. The bottom edge 32 a of the plate 32 exertsa compression force on the top of the ridge, said bottom edge being aportion of a surface that is cylindrical (in the broad sense of theterm) with generator lines that are parallel to the axis of rotation ofthe tools. As a result of the bumping of the machine, lateral parasiticforces induce bending and shearing forces which tend to cause the ridgeto rupture.

With very hard rocks, the reaction of the ridge against the drillingmachine can take up a large fraction, or even all, of the thrust forceexerted by the weight of the machine, thereby limiting the effectivenessof the rotary drilling tools corresponding.

OBJECTS AND SUMMARY OF THE INVENTION

An object of the present invention is to provide a drilling machine ofthe above-mentioned type which makes it possible to improve theprogressive disintegration of the ridge so as to improve the overalleffectiveness of the drilling machine, in particular when drilling hardground.

The invention achieves this object by providing a drilling machinecomprising a frame; at least one pair of rotary drilling tools havingsubstantially the same axis of rotation; and a support assembly securedto the frame and supporting said pair of tools in rotation, said supportassembly presenting an edge facing the cutting face and extendingbetween the tools of said pair of tools, said machine further comprisingmeans mounted on said support assembly for creating at least one jet ofliquid at very high pressure directed towards the cutting face betweenthe action zones of said pair of tools; whereby said jet of liquid atvery high pressure breaks up the ridge which forms in the cutting facebetween the action zones of said pair of rotary tools.

It should be understood that by means of the presence of the very highpressure jet(s) of liquid which is/are directed towards the ridge,breaking up of said ridge is improved very substantially compared to thesole compression action of the edge of the support assembly for therotary tools. Improved breaking up of the ridge tends to improve theoverall effectiveness of the tool.

The jet-creation means preferably comprise at least one nozzle suppliedwith very high pressure liquid, and opening out into said edge of thesupport assembly.

In an improved embodiment of the invention, said edge of theabove-defined drilling machine presents, at least over a portion of itslength, a face that is not symmetrical about said mid-plane, wherebysaid asymmetrical face exerts a bending force on the ridge formedbetween the action zones of said pair of tools, so as to break up saidridge.

It should be understood that as a result of at least one portion of theedge of the support assembly presenting a face that is not symmetricalabout the mid-plane of the support element, i.e. about the drillingdirection facing the ridge which tends to form between the rotary toolsof a same pair, mechanical bending action is exerted on the ridge by theface because of its orientation, which is more favorable todisintegration than a compression action since, as indicated above, theridge is weaker in bending than in compression.

The term “face of a portion of the rim” of the support element refersequally to a surface that is plane as to a surface that is skew.

It should also be understood that in this improved embodiment, thedisintegration of the ridge results from combining the action of thevery high pressure jets, and the mechanical bending action of theinclined edge of the support assembly on the ridge.

BRIEF DESCRIPTION OF THE DRAWINGS

Other characteristics and advantages of the invention appear better onreading the following description of several embodiments of theinvention given by way of non-limiting example.

The description refers to the accompanying figures in which:

FIG. 1, described above, is an overall view of a drilling vehicle;

FIG. 2, described above, is a view showing the bottom portion of thedrilling machine, with a portion of a pair of drilling tools beingremoved;

FIG. 3, described above, is a simplified side view showing a pair ofdrilling tools and their action on the cutting face;

FIG. 4 is a side view of the support assembly for supporting thedrilling tools equipped with nozzles for producing high-pressure jets;

FIG. 4A is a view of a detail of FIG. 4 showing the supply of thejet-producing nozzles.

FIG. 4B is a detail view of FIG. 4A showing the structure of a nozzle;

FIG. 5 is a perspective view of the edge of the support assemblyconstituting an improved embodiment of the invention;

FIG. 5A is a side view showing the edge of the support element;

FIG. 6 is a view from below showing a variant embodiment of the edge ofthe support element; and

FIG. 6A is a section view on line A-A of FIG. 6.

MORE DETAILED DESCRIPTION

A preferred embodiment of the invention is described below withreference firstly to FIGS. 4, 4A, and 4B.

FIG. 4 shows the plate 32 fixed onto the bottom end of the frame 20 a ofthe drilling machine, and onto which plate the pair of tools 26, 28 aremounted and supported. The plate includes a central recess 50 formounting motors and drums carrying the drilling elements. The figureshows the supply lines 52 for supplying liquid under pressure to thedrive motors of the drilling tools. In simplified manner, FIG. 4 showsnozzles such as 54 for creating very high pressure jets of liquid whichare provided in the edge 32 a of the plate 32 facing the cutting face40, and more precisely the ridge 42. The nozzles therefore produce jets56 of liquid under pressure that are directed towards the ridge over itsentire length, i.e. its extent along the direction that is perpendicularto the plane of FIG. 3.

As shown in FIG. 4A, the nozzles 54 are preferably supplied by supplylines such as 57, formed in the thickness of the plate 32. The nozzlesupply lines 57 are connected to hydraulic supply hoses 58 mounted inparallel with the main supply hoses for powering the hydraulic motors.

As shown more clearly in FIG. 4B, the nozzles 54 are mounted inside theplate 32 in such a manner that their outlets 54 a are set back from thebottom edges 32 a of the plate 32. For this purpose, holes 58 arepierced in the edge of the plate 32 to enable the high-pressure jetsdelivered by the nozzles 54 to be expelled.

The pressure of the liquid serving to create the jets preferably lies inthe range 100 mega pascals (MPa) to 200 MPa.

It should thus be understood that by means of the presence of the jetscreated by the nozzles 54, it is possible to cause the ridge 42 todisintegrate as fast as it is being formed, in particular if the groundthat is being drilled is hard.

An improved embodiment of the drilling machine is described below withreference to FIGS. 5 and 5A. In this improved embodiment, in order tobreak up the ridge, the high pressure jets are accompanied by amechanical bending effect on the ridge.

To achieve this result, the bottom edge 32 a of the plate 32 is nolonger constituted by a cylindrical surface having generator lines thatare perpendicular to the drilling direction, but by a succession ofpreferably alternating faces that are not symmetrical about themid-plane P, P′ of the plate 32. The faces can consist of plane surfacesor skew surfaces. To do this, prism-shaped elements such as 60 arepreferably fixed on the edge proper 32 a of the plate 32, each of saidelements presenting an active face 62 which forms an angle relative tothe drilling direction F, which angle lies in the range 30° to 60°, andis preferably equal to 45°. The prismatic elements 60 are alsopreferably disposed in alternation about the mid-plane P, P′ of theplate 32 in such a manner that the active faces 62 are alternately onopposite sides of the mid-plane P, P′. By means of their sloping faces62, the prismatic parts exert on the ridge, a force that is notperpendicular to the top of the ridge, but that is inclined relative tosaid ridge, thereby enabling a bending force to be applied to the ridge,tending to disintegrate it.

The nozzles 54 are thus mounted in the prismatic parts 60, and thesupply lines extend into said parts.

It should thus be understood that the ridge breaks up as a result of thecombination of the hydraulic action of the jets created by the nozzles54, and the mechanical action of the sloping faces 62 of the prismaticparts 60 mounted on the edge 32 a of the plate 32. A further improvementis thus obtained in breaking up the ridge that appears in the cuttingface, and thus an overall improvement in the effectiveness of thedrilling machine, in particular when the ground is very hard.

FIGS. 6 and 6A show a variant embodiment of the parts enabling bendingforce to be applied to the ridge 42.

In this embodiment, the prismatic parts 70 fixed on the edge 32 a of theplate 32 have a trapezoidal right section having an active small base 72of small size.

The longitudinal axes x, x′ of the parts 70 form an angle b relative towith the mid-plane P, P′ of the plate 32. The angle b lies in the range30° to 60°, for example.

In the above description, consideration is given to a drilling machine,usually referred to as a “cutter”. The invention can very well beapplied to other machines so long as the machine includes at least onepair of rotary tools whose action on the cutting face leads to a ridgebeing formed.

1. A drilling machine comprising: a frame; at least one pair of rotarydrilling tools having substantially the same axis of rotation; a supportassembly secured to the frame and supporting said pair of tools inrotation, said support assembly presenting an edge facing the cuttingface and extending between the tools of said pair of tools; and meansmounted on said support assembly for creating at least one jet of liquidat very high pressure directed towards the cutting face between theaction zones of said pair of tools; whereby said jet of liquid at veryhigh pressure breaks up the ridge which forms in the cutting facebetween the action zones of said pair of rotary tools.
 2. A drillingmachine according to claim 1, wherein the jet-creation means comprise atleast one nozzle supplied with very high pressure liquid, and openingout into said edge of the support assembly.
 3. A drilling machineaccording to claim 2, wherein the supply means for supplying said nozzlecomprise at least one supply channel formed in said support assembly. 4.A drilling machine according to claim 3, including a plurality ofnozzles and a plurality of supply channels.
 5. A drilling machineaccording to claim 1, wherein, at least over a portion of its length,said edge presents a face that is not symmetrical about the mid-plane ofsaid support assembly, whereby said asymmetrical face exerts a bendingforce on the ridge formed between the action zones of said pair oftools, so as to break up said ridge.
 6. A drilling machine according toclaim 5, wherein said face occupies substantially the entire width ofsaid edge, and makes an angle lying in the range 30° to 60° relative tothe drilling direction.
 7. A drilling machine according to claim 5,wherein said edge includes a plurality of asymmetrical faces.
 8. Adrilling machine according to claim 7, wherein said faces are inclinedrelative to the drilling direction in alternating directions.
 9. Adrilling machine according to claim 1, wherein the or each face isconstituted by a prism-shaped part fixed to the edge of the supportassembly.